The present invention relates to voltage regulators and, more particularly, to the use of the utility winding and a control unit in ANSI Type “A” Voltage Regulators to calculate the load voltage without the need of an embedded potential transformer.
A voltage regulator can be thought of as an autotransformer that regulates a secondary voltage. If there is a primary voltage that has a tendency to fluctuate, a voltage regulator will produce a constant secondary voltage. For instance, if a primary, or input, voltage fluctuates between 110 volts and 130 volts, the voltage regulator will maintain the secondary, or output, voltage at a constant 120 volts. Usually, a voltage regulator can increase or decrease its output voltage by up to 10% of its input voltage in ⅝% steps. The voltage regulator is equipped with a control unit which monitors the input and output voltages of the voltage regulator and moves the tap changer by the ⅝% steps to maintain a specified output voltage.
Typically, an ANSI load-side series winding, or Type “A,” voltage regulator uses a separate potential transformer to sense the load voltage and feeds that voltage to the control unit so that the control unit can change the tap position as needed. FIG. 1 illustrates the typical physical connection of a voltage regulator 100 with an embedded potential transformer 60. The potential transformer 60 is connected between the “L” and “SL” bushings. For example, the source voltage across the S and SL bushings may fluctuate between about 6900 volts and about 8300 volts. The load voltage is then stepped down by the potential transformer 60 to approximately 120 volts (or roughly between about 110 volts to about 130 volts). The control unit (not shown) then changes the tap position in response to the stepped down source voltage which results in the output voltage across the L and SL bushings of a constant 7620 volts.
FIG. 2 illustrates a block diagram of the flow of information to the control unit in a typical embodiment of a voltage regulator that contains an embedded potential transformer. In block 130, the voltage regulator feeds the input voltage to the control panel. In addition, in step 140, the output voltage from the embedded potential transformer supplies the output voltage to the control panel. The control panel, in step 150, in turn monitors the input and output voltages and adjusts position of the tap in order to adjust the output voltage as needed.
However, a need exists to simplify a voltage regulator by eliminating some of its components. By eliminating components of the voltage regulator, the material and manufacturing costs are reduced. In addition, the reliability of ANSI Type A voltage regulator increases with the reduction of components.